Multi-sectional swellable packer

ABSTRACT

A multi-sectional swellable packer for a wellbore has a mandrel and multiple packer elements mounted on the mandrel. The packer elements are formed of swellable materials that swell when contacted with a swelling fluid. In various embodiments, the outer diameter of the central element is larger than that of the end elements with or without gap between elements. In other embodiments, a multi-sectional swellable packer for a wellbore has multiple mandrels with multiple packer elements which are interconnected by flexible joints/connections. The outer diameter of the central element can be different from that of the end elements. The swellable rubber of the central element can be different from that of the end elements. The packer increases flexibility of operation and reduces the risk of run-in-hole.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to U.S. Provisional Application No.62/401,407, filed Sep. 29, 2016, herein incorporated by reference in itsentirety.

FIELD

The disclosure relates generally to a wellbore system for oilexploration. The disclosure relates specifically to a packer for awellbore system.

BACKGROUND

Many wellbore systems include a packer, which is designed to expandradially outwardly from a pipe against the wall of the wellbore. Thepacker is intended to seal segments of the pipe against wellbore inorder to isolate some sections of the wellbore from others. Knownsealing members for packers include mechanical packers which arearranged in the borehole to seal an annular space between a wellborecasing and a production pipe extending into the borehole. Such a packeris radially deformable between a retracted position, in which the packeris lowered into the borehole, and an expanded position, in which thepacker forms a seal.

In horizontal laterals, especially long ones, cementing can be verydifficult and can easily damage the formation. It, therefore, brings theopportunities to open-hole fracturing. In Open-hole completion,swellable packer can be used to seal irregular well bores in open holes.

Operationally, the benefit of a swellable packer is simplicity. There isno moving part required to work, through pipe manipulation or byapplying hydraulic pressure. No special service personnel are needed.The packers are simply run to depth, similar to the casing, and allowedto swell before production or injection operations begin.

Pressure rating of swellable rubber is typically low per unit length. Alengthy swellable rubber is needed to hold the specific differentialpressure.

In general, each foot of swellable rubber provides 1 ksi differentialpressure. In order to achieve 10 ksi differential pressure, it isrequired the swellable packer to be at least 12 feet. The lengthyswellable rubber brings up the difficulty and risk of run-in-hole. Inthe meantime, however, the real pressure rating required from the fieldmay not be as high as 10 ksi. It is, therefore, a need of flexibility ofoperation if there is a multi-section swellable packer.

Both ends of a long rubber swell and come into contact with the wellbore earlier than the rest due to their full contact with the fluid atthe ends. On the other hand, the swelling capability of rubber in themiddle is delayed since the absorption of water from brine by the rubberincreases the salinity of the surrounding brine. Since the rubber at thetwo ends contact with the wall first, the middle of most of the rubberlacks sufficient contact with fresh brine. The delayed swelling in themiddle forms a “saddle” effect. As an overall impact, the swellingefficiency and pressure rating of a swellable packer with lengthy rubberis negatively affected.

Running a multi-mandrel packer in a hole provides flexibility. Thelength of the packer can be adjusted by changing the number of mandrelsin the pack, such that the length of the packer can match the pressurerequired from the field. Furthermore, when the connection is flexible,the multi-mandrel packer can be easier to run-in-hole than a one mandrelpacker, especially in a long horizontal well where the well boretrajectory is torturous, because each mandrel in a multi-mandrel packeris much shorter than the mandrel in one mandrel packer.

SUMMARY

An embodiment of the disclosure is a packer comprising: a mandrel; and aplurality of packer elements mounted on the mandrel; wherein the packerelements comprise end elements and a central element arranged betweenthe end elements; wherein the packer elements are formed of swellablematerial that swells when contacted with a swelling fluid. In anembodiment, the outer diameter of the central element is different thanthat of the end elements. In an embodiment, the outer diameter of thecentral element is larger than that of the end elements. In anembodiment, the outer diameters of the central element and end elementsare increased gradually along the direction from ends to the center ofthe mandrel. In an embodiment, the packer elements abut each other. Inan embodiment, gaps exist between the packer elements. In an embodiment,the central element and end elements are formed of a unitary packermember.

An embodiment of the disclosure is a packer comprising: a plurality ofmandrels having the same inner diameter; a plurality of connectionelements coupled to the plurality of mandrels; a plurality of packerelements that circumferentially fit over the mandrels, wherein theplurality of packer element each have an outer diameter; and wherein thepacker elements are formed of a swellable material. In an embodiment,the plurality of connection elements can connect adjacent mandrels inthe plurality of mandrels. In an embodiment, the connection elements areflexible connections. In an embodiment, the connection elements arescrew type closure structures. In an embodiment, the screw type closurestructure comprises a male threaded member; a female threaded member;wherein the male threaded member and the female threaded member arescrewed into a complementary threaded engagement. In an embodiment, agullet is set below the normal root portion of at least one of twomating threads and wherein a flank of at least one of the mating threadsis crowned. In an embodiment, when the mandrels connect with each otherto form a multi-mandrel packer wherein the outer diameter of the centerpacker element is different the outer diameter of the end packerelement. In an embodiment, the outer diameter of the central packerelement is larger than the outer diameter of the end packer element. Inan embodiment, when the mandrels connect with each other to form amulti-mandrel packer wherein the swellable materials of the packerelements have different swelling speeds. In an embodiment, the swellingspeed of the center packer element is faster than the swelling speed ofthe end packer element.

An embodiment of the disclosure is a method of manufacturing the packerabove comprising vulcanizing different materials on a mandrel to formpacker elements; and machining the packer elements to form differentouter diameters.

As a first aspect, embodiments of the present disclosure are directed toa multi-sectional swellable packer for a wellbore. The packer comprisesa mandrel and multiple packer elements mounted on the mandrel. Thepacker elements are formed of swellable material that swells whencontacted with a swelling fluid.

In one embodiment, select a fast swelling rubber in the center of themandrel and select a slow swelling rubber in the ends of the mandrel.

In another embodiment, make large outer diameter (OD) of the rubber inthe center and make small OD of the rubber in the ends of the mandrel.

As a second aspect, embodiments of the present disclosure are directedto a multiple mandrels swellable packer for a wellbore. The packercomprises multiple mandrels having the same inner diameter, connectionelements coupled to the mandrels which can connect adjacent mandrels,packer elements that fit circumferentially over the mandrels and areformed of swellable material, and each packer element having an outerdiameter.

In one embodiment, the connection elements are a screw type closurestructure, a male threaded member and a female threaded member screwedinto a complementary threaded engagement, a gullet set below the normalroot portion of at least one of the two mating threads, and the flank ofat least one of said mating threads being crowned.

In another embodiment, the outer diameter of the center packer elementis larger than that of the end packer element.

In yet another embodiment, the swellable materials of the packerelements have a different swelling speed. The swelling speed of thecenter packer element is faster than that of the end packer element.

In another embodiment, the manufacturing process of multi-sectionswellable packer is to vulcanize the different materials on one mandrelfollowed by OD machining. After machining, the rubbers are bondedstrongly on the mandrel.

The present disclosure can significantly improve the sealing efficiencyof the packer by multi-section packers with different rubber materials,different OD and specially designed connection, improve effectivesealing area of the swellable rubber by increasing the sealing pressureper unit of length of the rubber, Improve the flexibility ofrun-in-hole, and improve the flexibility of assembly of multiplesections on the well site, reducing the challenge of run-in-hole andsaving the overall cost.

By applying the multi-sectional swellable packer, the sealing efficiencyof the packer will significantly improve by multi-section packers withdifferent rubber materials, different OD and specially designedconnection; improve effective sealing area of the swellable rubber byincreasing the sealing pressure per unit of length of the rubber;improve the flexibility of run-in-hole; improve the flexibility ofassembly of multiple sections on the well site, reducing the challengeof run-in-hole and saving the overall cost.

The foregoing has outlined rather broadly the features of the presentdisclosure in order that the detailed description that follows may bebetter understood. Additional features and advantages of the disclosurewill be described hereinafter, which form the subject of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and otherenhancements and objects of the disclosure are obtained, a moreparticular description of the disclosure briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the disclosure and are therefore notto be considered limiting of its scope, the disclosure will be describedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 shows a swellable packer annular seal in an irregular holes;

FIG. 2 shows a multi-section swellable packer in a prior art;

FIG. 3 shows another multi-section swellable packer in a prior art;

FIG. 4 shows stacking water swell sleeves: 2 ft. and 3 ft. elements tohold 5 ksi in a prior art;

FIG. 5 shows a SwellFix Packer that can hold up to 10 ksi, depending onthe rubber length combination in the prior art;

FIG. 6 shows a saddle effect of a swellable packer in the prior art;

FIG. 7 shows a multi-section swellable packer with a large outerdiameter in the center and without a gap between sections;

FIG. 8 shows a swellable packer with a gradual outer diameter change;

FIG. 9 shows a multi-section swellable packer with a large outerdiameter in the center and having gaps between sections;

FIG. 10 shows a multi-section swellable packer with gradual outerdiameter change and having a gap between sections;

FIG. 11 shows a multi-section swellable packer with different diameterrubber;

FIG. 12 shows a multi-mandrel swellable packer with flexiblejoints/connections;

FIG. 13 shows the connection of FIG. 12;

FIG. 14 shows a multi-mandrel swellable packer with connections; and

FIG. 15 shows the multi-stage fracturing using a multi-mandrel swellablepacker.

DETAILED DESCRIPTION

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentdisclosure only and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of various embodiments of thedisclosure. In this regard, no attempt is made to show structuraldetails of the disclosure in more detail than is necessary for thefundamental understanding of the disclosure, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the disclosure may be embodied in practice.

The following definitions and explanations are meant and intended to becontrolling in any future construction unless clearly and unambiguouslymodified in the following examples or when application of the meaningrenders any construction meaningless or essentially meaningless. Incases where the construction of the term would render it meaningless oressentially meaningless, the definition should be taken from Webster'sDictionary 3^(rd) Edition.

In an embodiment, the multi-section swellable packer can comprise acombination of different swellable rubbers and connection designs. In anembodiment, the multi-section swellable packer possesses high efficiencyof swellable rubber per unit length and high flexibility of assembly atthe well site. In an embodiment, the difficulty and the risk ofswellable packer run-in-hole process is reduced. In an embodiment, theE&P efficiency of hydrocarbons from formations with low pressure, lowpermeability, and low abundance is improved by increasing the fracturingefficiency using the multi-section swellable packer.

FIG. 1 shows a swellable packer annular seal in irregular holes. Theseal is formed of swellable elastomer. The elastomer expands radiallywhen exposed to an activating liquid, such as water or hydrocarbon.Exemplary elastomer materials that swell in hydrocarbon include but arenot limited to ethylene propylene rubber (EPM and EPDM),ethylene-propylene-diene terpolymer rubber (EPT), butyl rubber,brominated butyl rubber, chlorinated butyl rubber), chlorinatedpolyethylene, neoprene rubber, styrene butadiene copolymer rubber (SBR),sulphonated polyethylene, ethylene acrylate rubber, epichlorohydrinethylene oxide copolymer, silicone rubbers and fluorsilicone rubber.Exemplary materials that swell in water include starch-polyacrylate acidgraft copolymer, polyvinyl alcohol cyclic acid anhydride graftcopolymer, isobutylene maleic anhydride, acrylic acid type polymers,vinylacetate-acrylate copolymer, polyethylene oxide polymers,carboxymethyl cellulose type polymers, starch-polyacrylonitrile graftcopolymers and the like and highly swelling clay minerals such as sodiumbentonite. The shape of the annular seal can adapt to irregular holes.

FIG. 2 depicts a Q-Seal multi-section vulcanized swellable packer byRuma Rubber. FIG. 3 depicts a Q-Stax multi-section slide-on swellablepacker by Ruma Rubber. They use the same rubber with the same outerdiameter (OD) and have space or a space ring between the sections. Bothends of a rubber swell come into contact with the well bore earlier thanthe rest due to their full contact with the fluid at the ends. On theother hand, the swelling capability of rubber in the middle is delayedsince the absorption of water from brine by the rubber increases thesalinity of the surrounding brine. Since the rubber at the two endscontacts with the wall first, the middle of most of the rubber lackssufficient contact with fresh brine.

FIGS. 4 and 5 show Stacking Water Swell Sleeves and SwellFixmulti-section swellable packer by Tendeka. In an embodiment, the samerubber is used with the same OD. In an embodiment, there is a spacer orspacer ring between the sections. FIG. 4 shows stacking water swellsleeves: 2 ft. and 3 ft. elements to hold 5 ksi. FIG. 5 shows a SwellFixPacker that can hold up to 10 ksi, depending on the rubber lengthcombination.

FIG. 6 depicts that the delayed swelling in the middle forms a “saddle”effect. As an overall impact, the swelling efficiency and pressurerating of swellable packer with lengthy rubber is negatively affected.

FIG. 7 shows a multi-section swellable packer with a large outerdiameter in the center. The swellable packer includes a mandrel andmultiple packer elements mounted on the mandrel. The packer elements areformed of swellable material that swells when contacted with a swellingfluid. A large outer diameter swelling element is present in the centerof the mandrel and two small outer diameter swelling rubbers are presentat the both ends of the mandrel. There is no gap between the swellableelements. In an embodiment, the packer comprises one mandrel made of onematerial.

FIG. 8 shows a swellable packer with gradual outer diameter change inaccordance with one embodiment of the present disclosure. In thisembodiment, the swellable packer includes a mandrel and a packer elementmounted on the mandrel, the packer element is formed of a singlematerial, but it is tapered, such that it has a larger central portionand narrow ends. Thus, when the packer element is contacted with anactivating liquid, the central portion and the ends may swell, but thecentral portion seals the wall more rapidly than the ends, which avoidsforming a “saddle” in the packer. In another embodiment, for example inFIG. 10, the swellable packer in FIG. 8 can be separated into aplurality of elements which have gaps between them. In an embodiment,the packer comprises one mandrel made of one material.

Select the fast swelling rubber in the center; select the slow swellingrubber in the ends; make large OD of the rubber in the center; and makesmall OD of the rubber in the ends. The manufacturing process of amulti-section swellable packer is to vulcanize the different materialson one mandrel followed by OD machining. After machining, the rubbersare bonded strongly on the mandrel.

FIG. 9 depicts a multi-section swellable packer with a large outerdiameter in the center. The swellable packer includes a mandrel andmultiple packer elements mounted on the mandrel. The packer elements areformed of swellable material that swells when contacted with a swellingfluid. A large outer diameter swelling element is present in the centerof the mandrel and two small outer diameter swelling rubbers are presentat both ends of the mandrel. In some embodiments, gaps may exist betweenthe swellable elements (FIG. 9). In an embodiment, the packer comprisesone mandrel made of one material.

FIG. 10 shows a multi-section swellable packer with different diameterrubber. The swellable packer includes a mandrel and multiple packerelements mounted on the mandrel. The packer elements are formed of aswellable material that swells when contacted with a swelling fluid. Inan embodiment, the packer includes a center element with a large outerdiameter in the center and a decreasing outer diameter toward the endsof the center element. There are two end elements that are directly orindirectly adjacent to the center element. The two end elements have adecreasing outer diameter away from the center element. The largestouter diameter of the end elements is smaller than the smallest outerdiameter of the center element. The elements may abut each other or havegaps between adjacent elements. When contacted with activating liquid,the center element swells and takes less time to contact and sealagainst the wall of wellbore than the end elements. Thus the centerelement can sufficiently swell to seal against the wall. In anembodiment, the packer comprises one mandrel made of one material.

A conventional single element swellable packer swells fast at the ends.After the two ends contact the well bore or casing, the rubber in thecenter is swelling by diffusion which is slow and affects the swellingrate of the whole packer. By using different rubber materials, it allowsswelling faster in the center so that the whole packer can evenly andthoroughly swell. Similarly, with a larger OD in the center than theend, the rubber in the center can contact the well bore or casingearlier so that the whole packer can finish swelling evenly andthoroughly.

FIG. 11 shows a multi-section swellable packer with different diameterrubber.

FIG. 12 shows a multi-mandrel swellable packer with flexiblejoints/connections.

In another embodiment, a multiple mandrel swellable packer for awellbore is provided. Referring to FIG. 12, the packer comprisesmultiple mandrels having the same inner diameter, connection elementscoupled to the mandrels which can connect adjacent mandrels, packerelements that fit circumferentially around the mandrels and are formedof swellable material, and each packer element having an outer diameter.

In an embodiment, the multiple mandrel swellable packer of FIG. 13 hasthe same OD and same material.

In an embodiment, the multiple mandrel swellable packer of FIG. 13 hasthe same OD and a different material (faster swelling in center, slowerswelling in ends)

In an embodiment, the multiple mandrel swellable packer of FIG. 13 has adifferent OD (larger OD in center, smaller OD in ends) and the samematerial

In an embodiment, the multiple mandrel swellable packer of FIG. 13 has adifferent OD (larger or smaller OD in center) and a different material(faster or slower swelling in center). The final goals of thesecombinations are to make the swelling even in order to evenly set ontothe well bore from the ends to the center of the packer.

FIG. 13 shows a possible connection for FIG. 12. FIG. 13 is found inU.S. Pat. No. 3,487,442, directed to flexible thread systems for highpressure vessels and the like. Referring to FIG. 13, the connectionelements are screw type closure structures, a male threaded member and afemale threaded member are screwed into a complementary threadedengagement. A gullet is set below the normal root portion of at leastone of the two mating threads, the flank of at least one of said matingthreads being crowned. The connections are designed for high bendingflexibility and are manufactured to prevent unwanted back-off failures.Stress reliefs in the packer minimize bending loads on the break pointallowing high flexibility.

FIG. 14 shows a multi-mandrel swellable packer in an embodiment withflexible joints which was applied on a drilling tool made by TTSDrilling Solutions who stated “Safety Joints are designed for highbending flexibility. They are manufactured with a proprietary threaddesigned to prevent unwanted back-off failures. Stress reliefs in thetools minimize bending loads on the break point allowing highflexibility.” Available athttp://www.ttsdrilling.com/Products-Solutions/Safety-Joints.aspx.Referring to FIG. 14, the packer comprises multiple mandrels having thesame inner diameter, connection elements coupled to the mandrels whichcan connect adjacent mandrels, packer elements that fitcircumferentially around the mandrels and are formed of swellablematerial, and each packer element having an outer diameter.

FIG. 15 shows multi-stage fracturing using a multi-mandrel swellablepacker.

In an embodiment, packer elements of a multiple mandrel swellable packerhave the same outer diameter and are made of the same material. Thoseskilled in the art will appreciate that other embodiments may also besuitable. For example, they can have the same outer diameter anddifferent materials, such as the swelling speed of the center packerelement is faster than that of the end packer element. As analternative, they can have the same material and different outerdiameters, but the outer diameter of the center packer element is largerthan that of the end packer element. In yet another embodiment, thepacker elements can have different outer diameters and can be made ofdifferent materials. There can be larger or smaller outer diameter incenter, and there can be faster or slower swelling speed material incenter.

The multiple mandrel swellable packer makes it possible for flexibleselection of section amounts based on requirements from the wellbore.The specially designed connection can provide sufficienttension/compression as well as sealing capability.

In an embodiment of the manufacturing process, each section isvulcanized individually. Each section can have the same or differentrubber materials, and the same or different ODs. They are connectedlater when needed.

In an embodiment, there is a multi-mandrel with specially designedconnection with sealing capability. In an embodiment, there is flexibleselection of section amounts based on requirements from the wellbore. Inan embodiment, there is a specially designed connection to providesufficient tension/compression as well as sealing capacity. In anembodiment in the manufacturing process, each section is vulcanizedindividually. Each section can have the same or different rubbermaterials and the same or different ODs. They are connected later whenneeded.

Conventional swellable packers for fracturing are normally lengthy,which causes difficulty or risk during run-in-hole. Using multi-mandreldesign, the properly selected length will be determined on-site to meetthe specific wellbore requirement (referring to FIGS. 12 and 14). It canpossibly save the length of rubber, and save the difficulty or riskduring run-in-hole. Specially designed connections can be tubing jointsor modified ball bearing connections, or the like. With moreconnections, the overall packer increases the flexibility and reducesthe risk of run-in-hole.

EXAMPLES Example 1

A large amount of rubber materials and ODs will be tested. Materialselection will be carefully conducted.

Example 2

The design of the special connection will be easily assembled in thefield and needs sealing capability.

All of the compositions and methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the compositions and methods of this disclosure havebeen described in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to thecompositions and methods and in the steps or in the sequence of steps ofthe methods described herein without departing from the concept, spiritand scope of the disclosure. More specifically, it will be apparent thatcertain agents which are both chemically related may be substituted forthe agents described herein while the same or similar results would beachieved. All such similar substitutes and modifications apparent tothose skilled in the art are deemed to be within the spirit, scope andconcept of the disclosure as defined by the appended claims.

What is claimed is:
 1. A packer comprising: a mandrel; and a pluralityof packer elements mounted on the mandrel; wherein the packer elementscomprise end elements and a central element arranged between the endelements; wherein the packer elements are formed of swellable materialthat swells when contacted with a swelling fluid.
 2. The packer of claim1, wherein the outer diameter of the central element is different thanthat of the end elements.
 3. The packer of claim 2, wherein the outerdiameter of the central element is larger than that of the end elements.4. The packer of claim 1, wherein the outer diameters of the centralelement and end elements are increased gradually along the directionfrom ends to the center of the mandrel.
 5. The packer of claim 1,wherein the packer elements abut each other.
 6. The packer of claim 5,wherein gaps exist between the packer elements.
 7. The packer of claim3, wherein the central element and end elements are formed of a unitarypacker member.
 8. A packer comprising: a plurality of mandrels havingthe same inner diameter; a plurality of connection elements coupled tothe plurality of mandrels; a plurality of packer elements thatcircumferentially fit over the mandrels, wherein the plurality of packerelement each have an outer diameter; and wherein the packer elements areformed of a swellable material.
 9. The packer of claim 8 wherein theplurality of connection elements can connect adjacent mandrels in theplurality of mandrels.
 10. The packer of claim 8, wherein the connectionelements are flexible connections.
 11. The packer of claim 9, whereinthe connection elements are screw type closure structures.
 12. Thepacker of claim 11 wherein the screw type closure structure comprises amale threaded member; a female threaded member; wherein the malethreaded member and the female threaded member are screwed into acomplementary threaded engagement.
 13. The packer of claim 12 wherein agullet is set below the normal root portion of at least one of twomating threads and wherein a flank of at least one of the mating threadsis crowned.
 14. The packer of claim 8 wherein when the mandrels connectwith each other to form a multi-mandrel packer wherein the outerdiameter of the center packer element is different the outer diameter ofthe end packer element.
 15. The packer of claim 14, wherein the outerdiameter of the central packer element is larger than the outer diameterof the end packer element.
 16. The packer of claim 8, wherein when themandrels connect with each other to form a multi-mandrel packer whereinthe swellable materials of the packer elements have different swellingspeeds.
 17. The packer of claim 16, wherein the swelling speed of thecenter packer element is faster than the swelling speed of the endpacker element.
 18. A method of manufacturing the packer of claim 3comprising vulcanizing different materials on a mandrel to form packerelements; and machining the packer elements to form different outerdiameters.